Conventionally, among electrical systems for an automobile that supply electric power to an electrical device from a direct-current power source via a semiconductor power converter, there has been an electrical system for automobiles that uses an electric wire that is formed by having successively concentrically formed from a center, an electric conductive material, a first insulating material, a sheet electrostatic shielding material, a second insulating material, and a sheet magnetic shielding material, for a wiring from the direct-current power source to the semiconductor power converter. In this conventional electrical system, a principal current is conducted to the electric conductive material, one end of the electrostatic shielding material is connected to a ground potential of the semiconductor power converter, and one end of the magnetic shielding material is connected to a casing of the semiconductor power converter (see, for example, Patent Document 1). A shield of this conventional electrical system is grounded at one side.
Patent Document 1: Japanese Patent Application Laid-open No. 2002-051403 (FIG. 1)